package zh.codegym.task.task05.task0507;

/* 
算术平均值
*/

import java.util.Scanner;

public class Solution {
    public static void main(String[] args) throws Exception {
        //在此编写你的代码
        Scanner scanner = new Scanner(System.in);
        double input,sum= 0,count=0;
        while ( -1 != ( input = scanner.nextInt()) && (count++)!=-1 ){
            sum += input;
        }
        System.out.println(sum/count);

    }
}

